In a vehicle, a turbocharger equipped with a compressor and a turbine are provided in an intake passage and an exhaust passage, respectively, to improve thermal efficiency of an internal combustion engine. In recent years, as one means to improve turbo lag and responsiveness of the turbocharger, the electric supercharger driven by the electric motor has attracted attention. However, the electric supercharger has many challenges in durability, ease of assembly and ease of installation at the time of installation to the vehicle.
From the viewpoint of reducing axial vibration, the electric supercharger is normally supported at both ends of a motor rotor, which is heavy in weight. The electric supercharger of this two end support method is disclosed in Patent Document 1. In reference to FIG. 8, this supporting method is described. A housing of the electric supercharger 100A is composed of a compressor housing 102, a motor housing 104 and bearing housings 106a and 106b provided on both sides of the motor housing 104. In the compressor housing 102, a compressor wheel 108 is accommodated. A rotation shaft 110 extends toward the motor housing 104 from the center of the compressor wheel 108.
A motor rotor 112 is attached to the rotating shaft 110. A stator (not shown) is provided inside the motor housing 104. The stator is disposed at a position facing the motor rotor 112. Inside the bearing housings 106a and 106b, bearings 114 for supporting the rotating shaft 110 are provided on both sides of the motor housing 104. An inlet 102a of the compressor housing 102 is connected to an intake passage of the internal combustion engine, and by rotation of the compressor wheel 108, supply air a is drawn into the compressor wheel 108 to compress and discharge the supply air a to the outlet side of the intake passage.
FIG. 9 illustrates an electric supercharger 100B for supporting the rotation shaft 110 by one end. In the electric supercharger 100B, a bearing housing 106 is provided between the motor housing 104 and the compressor housing 102. A plurality of bearings 114 is provided inside the bearing housing 106 so as to support the rotation shaft 110 by these bearings 114.